1. Technical Field
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a method of manufacturing a printing plate used for a printing method which is one of patterning methods, and a method of manufacturing an LCD device using the same.
2. Discussion of the Related Art
Among various ultra-thin flat type display devices, which include a display screen having a thickness of several centimeters, a liquid crystal display (LCD) device can be widely used for notebook computers, monitors, aircraft, and etc. since it has advantages such as low power consumption and portability.
The LCD device includes lower and upper substrates facing each other at a predetermined interval therebetween, and a liquid crystal layer formed between the lower and upper substrates.
The lower substrate comprises a gate line, a data line, and a thin film transistor. At this time, the gate line is formed in perpendicular to the data line, to define a unit pixel region. Then, the thin film transistor is formed adjacent to a crossing of the gate and data lines, wherein the thin film transistor serves as a switching device. In addition, a pixel electrode is connected with the thin film transistor.
The upper substrate comprises a black matrix layer for shielding the gate line, the data line and the thin film transistor from light, a color filter layer formed on the black matrix layer, and a common electrode or an overcoat layer formed on the color filter layer.
The above LCD device includes various elements formed by repeated steps. Especially, a photolithography is used so as to form the elements in various shapes.
For the photolithography, it is necessary to form a pattern material layer on a substrate, to deposit a photoresist on the pattern material layer, to position a mask of a predetermined pattern above the photoresist, and to pattern the photoresist according to the predetermined pattern of the mask by exposure and development. After that, the pattern material layer is etched using the patterned photoresist as a mask.
The photolithography necessarily uses the photoresist and the mask of the predetermined pattern, to thereby increase a manufacturing cost. In addition, since the photolithography requires exposure and development, it causes a complicated process and an increasing manufacturing time.
To overcome these problems of the photolithography, a new patterning method has been developed, for example, a printing method using a printing roller.
A patterning method using a printing roller according to the related art will be described with reference to the accompanying drawings.
FIGS. 1A to 1C are cross sectional views of illustrating a process for patterning a predetermined material on a substrate with a printing roller according to the related art.
As shown in FIG. 1A, first, a pattern material 30 is provided through a printing nozzle 10, and is coated on a printing roller 20.
Then, as shown in FIG. 1B, the printing roller 20 coated with the pattern material 30 rolls on a printing plate 40 having a plurality of concave and convex patterns. Accordingly, some pattern material 30b is printed on the convex patterns of the printing plate 40, and the other pattern material 30a is left on the printing roller 20. That is, a predetermined form of the pattern material is formed on the printing roller 20.
Referring to FIG. 1C, as the printing roller 20 having the pattern material of the predetermined pattern rolls on a substrate 50, the pattern material 30a is printed on the substrate 50.
The patterning method using the printing roller requires the printing plate having the predetermined concave and convex patterns.
A method for manufacturing a printing plate according to the related art will be described as follows.
FIGS. 2A to 2C are cross sectional views of illustrating a method for manufacturing a printing plate according to the related art.
As shown in FIG. 2A, a metal layer 60 is formed on a substrate 45. Then, a photoresist 61 is formed on the metal layer 60. Thereafter, the photoresist 61 is patterned by exposure and development. Then, the metal layer is selectively removed using the patterned photoresist 61 as a mask, to thereby form a mask layer 60a of a predetermined pattern.
Referring to FIG. 2B, after removing the photoresist 61, the substrate 45 is isotropically etched using the mask layer 60a, to thereby form a trench 70 in the substrate 45. At this time, the substrate 45 is etched in the isotropic method of wet-etching. Accordingly, some portions of the substrate 45 under the mask layer 60a may be removed since the substrate 45 is etched in a horizontal direction as well as in a vertical direction, thereby generating an undercut phenomenon.
Referring to FIG. 2C, the mask layer 60a is removed to thereby form a printing plate 40.
However, the method of manufacturing the printing plate according to the related art has the following disadvantages.
FIG. 3 is a cross sectional view of explaining a problem generated when forming the pattern with the printing plate according to the related art.
As explained in FIG. 2B, when forming the trench 70, the substrate 45 is isotropically etched. That is, the substrate 45 is etched in the horizontal direction as well as in the vertical direction, whereby the inner side surface of the trench 70 has a gentle slope.
Accordingly, when printing the pattern material 30b on the printing plate 40, the pattern material 30b is printed on the edges and inner surfaces of the trench 70. That is, it is difficult to print the precisely desired pattern on the printing roller 20.